In today's common rail diesel injection systems, the fuel pressure for injection is electronically regulated. A fuel metering unit is used as an actuator in the low-pressure zone upstream from the high-pressure pump. German Patent No. DE 19612413, for example, describes a fuel metering unit of this type.
At this time, methods for diagnosing a defective circuit of the fuel metering unit are known. They are only able to recognize errors that are present for a longer time. Transient errors, for example, a brief intermittent contact, cannot be recognized.